Toughened polymer compositions

ABSTRACT

Toughened thermoplastic compositions comprising a thermoplastic polymer toughened by the inclusion of a thermoplastic elastomer derived from a particulate rubber dynamically vulcanized in the presence of a matrix polymer. The toughened thermoplastic composition exhibits properties including toughness, improved impact resistance, and improved hardness. The compositions are utilized wherever toughened, high performance polymers are desired. A method for forming the toughened polymer compositions is also described. Processing methods, such as rotational molding, utilizing the toughened polymer compositions are described.

CROSS REFERENCE

This application is a continuation-in-part of related application Ser.No. 10/754,045 filed Jan. 8, 2004, for TOUGHENED POLYMER COMPOSITIONS.

FIELD OF THE INVENTION

The present invention is directed to thermoplastic polymer compositions,which are toughened by the inclusion of a thermoplastic elastomercomponent comprising a particulate rubber component dynamicallyvulcanized in the presence of a matrix polymer. The toughened polymercompositions comprising a blend of a thermoplastic polymer component andthe crosslinked particulate elastomer in a matrix polymer exhibitproperties including toughness, improved impact resistance, and improvedhardness.

BACKGROUND OF THE INVENTION

Various polymer and rubber compositions, and combinations have beenproposed as an attempt to achieve desirable properties such as toughnessand rigidity for use in certain applications. One prior art approachteaches modification of a polymer by grafting rubber on the polymerchain backbone. A second approach involves the use of core and shellstructure as an impact modifier, wherein an elastomeric core issurrounded by a polymeric shell. A third approach involves physicallyblending an uncured elastomer and a thermoplastic.

With respect to the field of rotational molding, polymer processors mustcompromise between existing resins having either a sufficient hardnessor impact strength. Typical rubber modified polymers such as impactpolystyrene and ABS cannot be rotationally molded easily, or even atall. The rubber component is not stable during the relatively longmolding time cycles. Further problems include inconsistent, non-uniformmelt flow of the different polymer components of the blend, and moldedarticles exhibiting webbing and/or having rough surface textures.

Even though various elastomeric polymer combinations exist, the moldingand processing industry still seeks polymeric compositions which aretoughened and exhibit hardness and impact resistance, while beingprocessable in conventional equipment.

SUMMARY OF THE INVENTION

The toughened polymer compositions of the present invention are physicalblends of a thermoplastic polymer component and a thermoplasticelastomer or vulcanizate component. The elastomer component includes arubber component that is dynamically vulcanized in the presence of amatrix polymer prior to blending with the thermoplastic polymercomponent. Preferably, crystalline polymers are utilized as thethermoplastic polymer component. The toughened polymer compositionsoptionally contain fillers including nano-size fillers, flameretardants, lubricants, stabilizers, processing aids, colorants, orother additives. A method for preparing the toughened polymercompositions is described.

Unexpectedly, the toughened polymer compositions are impact resistantand exhibit high Rockwell “R” hardness. The toughened compositions areused in various applications, as well as processes such as extrusion,injection molding, blow molding, compression molding, thermoforming,rotational molding, or any other process where thermoplastic polymersare utilized.

In a further embodiment, the toughened polymer compositions are used toform rotationally molded articles which are impact resistant whilehaving excellent hardness. Methods for producing articles from thetoughened polymer compositions are described.

DETAILED DESCRIPTION OF THE INVENTION

The toughened polymer compositions of the invention comprise a blend ofa thermoplastic polymer component and a thermoplastic elastomer orvulcanizate component. The elastomer component is prepared bydynamically vulcanizing a rubber component in a blend also comprising amatrix polymer. The vulcanized rubber component is dispersed in thematrix polymer, and subsequently in the thermoplastic polymer component,as particles, preferably micron sized particles.

The thermoplastic polymer component of the toughened polymer compositiongenerally has an ordered or substantially ordered structure and is thuscrystalline or semicrystalline. The thermoplastic polymers utilized inthe toughened polymer compositions exhibit a relatively clear or sharpmelting point as well as a glass transition temperature (Tg).Conversely, amorphous polymers which are not preferred, exhibit only aTg and have no melting point.

Non-limiting specific examples of the crystalline or semi-crystallinethermoplastic polymer components used in the present invention arepolyolefins, polyamides, polyesters, halogen-containing thermoplasticssuch as polyvinylidene chloride, and the copolymers thereof. Blends ofthe thermoplastic polymers can be used. Compatibilizers are used to formcompatabilized blends where the polymers are not compatible.Polyolefins, polyamides and polyesters are preferred, with thepolyolefins being most preferred.

Examples of the polyolefins which are used as a thermoplastic componentin the present invention are polymers derived from linear or branchedolefin monomers having from 2 to about 14 carbon atoms, preferably from2 to about 6 carbon atoms or mixtures thereof, such as, but not limitedto, ethylene, propylene, butene, pentene, hexene, heptene,2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, and5-methyl-1-hexene.

In a preferred embodiment, the thermoplastic polymer component comprisesa homopolymer in an amount generally greater than 50% by weight,desirably from about 65% or about 80% to 100% by weight and preferablyfrom about 90% to 100% by weight based on the total weight of thethermoplastic polymer component. Thus, thermoplastic homopolymers arepreferred as opposed to the thermoplastic polymer component being acopolymer.

Polyolefins also include, but are not limited to, low densitypolyethylene, high density polyethylene, linear low densitypolyethylene, polypropylene (isotactic and syndiotactic), polybutene,and a copolymer of the greater part by weight of an olefin and a lesseramount of a vinyl monomer such as vinyl acetate. In a preferredembodiment, the polyolefin utilized in the thermoplastic polymercomponent is substantially free of functional groups. Of the definedolefinic polymers, polyethylene such as high-density polyethylene, andpolypropylene are preferred from the standpoint of moldingprocessibility, resistance to chemicals, cost, etc. Polyolefins arecommercially available from commercial sources including, but notlimited to, Chevron, Dow Chemical, DuPont, Exxon Mobil, HuntsmanPolymers, Ticona, and Westlake Polymer under various designations, invarious molecular weights and molecular weight distributions.

Examples of the polyamides which can be used in the present invention inone embodiment include, but are not limited to, polymers and copolymersformed by polycondensation of a diamine having from 4 to 12 carbonatoms, and a dibasic acid having from 4 to 12 carbon atoms,selfpolycondensation of an amino acid, or polymerization of a lactam,i.e. ring-opening polymerization. Specific examples of the polyamideinclude, but are not limited to, nylons such as nylon-4, nylon-4,6,polyhexamethyleneadipamide (nylon-6,6), polycaprolactam (nylon-6), nylon6,9, polyhexamethylenesebacamide (nylon-6,10), nylon-11, nylon-12 andcopolymers thereof. Polyamides are commercially available from sourcessuch as Albis, Clariant, Firestone, Ticona, Bayer, Ferro, DuPont andBASF under various designations. Preferred polyamides are nylon-6 andnylon-6,6 which are available from BASF, of Wyandotte, Mich. as theUltramide® series.

The polyesters which can be used in the present invention in oneembodiment are well known in the art and are linear polyesters or linearcopolyesters composed of a unit obtained by condensation-reaction of adicarboxylic acid either aromatic or aliphatic, or a derivative thereofhaving a total of from about 2 to about 16 carbon atoms; and a diol or aderivative thereof having a total of from about 2 to about 16 carbonatoms as the main structural component. Polyesters can also be preparedby self condensation of a hydroxy carboxylic acid, or ring openingpolymerization of a lactone. One can also introduce a small amount oftriol or a higher alcohol to promote branching. Examples of thepolyester include, but are not limited to, polyethylene terephthalate,polybutylene terephthalate, polyethylene isophthalate, and blockpolyetheresters such as one sold under the trade name “Hytrel”(available from DuPont). The preferred polyester, polybutyleneterephthalate, is available from GE Plastics, Pittsfield, Mass. asValox®. Polyesters are commercially available from sources such asAdell, BASF, Clariant, DuPont, Ticona, GE, and Noveon under variousdesignations.

The thermoplastic elastomer or vulcanizate (TPV) component of thetoughened polymer composition includes at least one cured elastomer orrubber component and at least one thermoplastic matrix polymer. Therubber component is crosslinked so that generally greater than about60%, and desirably greater than about 80% and preferably greater thanabout 95% by weight is insoluble in an appropriate solvent in which thenon-crosslinked rubber is soluble. The TPV component optionally containsadditional rubbers or elastomers which may or may not be dynamicallycrosslinked; or one or more thermoplastic matrix polymers; or acombination thereof.

The rubber component of the thermoplastic elastomer includes one or morerubbers. In one embodiment, the rubber component of the elastomercomprises a thermoplastic olefin rubber. Preferably the rubber componentcomprises a copolymer, i.e., two or more different alpha olefinmonomers, for example ethylene and propylene (EP or EPM rubber),1-butene, 1-hexene, 2-methyl-1-propene, 1-pentene, 3- or4-methyl-1-pentene or 1-octene. The monoolefin rubbers are saturated. Aterpolymer of two or more different alpha olefin monomers such asethylene or propylene, and at least one polyene, such as a diene monomer(EPDM rubber) has unsaturation sites for efficient crosslinking orvulcanization and is a preferred elastomer for use with olefinic matrixpolymers. The at least one diene monomer, is preferably non-conjugateddiene and generally has from 5 to about 20 carbon atoms, with about 6 toabout 12 carbon atoms being preferred. Examples of specific dienesinclude, but are not limited to, 1,4-pentadiene; 1,4-hexadiene; cyclicdienes such as cyclooctadiene and 1,3-cyclopentadiene; and bridgedcyclic dienes such as norbornene, 5-methylene-2-norbornene,5-ethylidene-2-norbornene, dicyclopentadiene, vinyl norbornene, and thelike; with norbornenes and dicyclopentadiene being desired, and ahexadiene such as 1,4-hexadiene and norbornenes being preferred. Theamount of the diene component utilized in the EPDM is from about 0.5 toabout 12 percent by weight and preferably from about 2 to about 8percent by weight based upon the total weight of the rubber formingmonomers, for example, the ethylene, the propylene, and the at least onediene monomer. EP rubber and EPDM rubber and the methods for producingthe same are well known in the art and are commercially available fromnumerous sources including, Dupont Dow, Bayer, DSM Elastomers, ExxonMobile, Nizh USA, and Uniroyal under various designations.

Other rubbers are used in the instant invention in some embodiments.They include styrene butadiene rubber, hydrogenated styrene butadienerubber, butyl rubber, butyl-paramethyl styrene copolymer and itsfunctionalized derivatives such as a brominated version or one that ismodified by acrylic monomers, and styrenic block copolymers such asSEBS, SEPS and SIBS which are crosslinked by peroxides with or withoutcoagents or other appropriate crosslinking agents. Other examples ofrubbers include, but are not limited to acrylic rubber, nitrile rubber,hydrogenated nitrile rubber, urethane rubber and ethylene methacrylateterpolymer rubber. Rubbers not compatible with the matrix polymer orthermoplastic polymer component require the use of a compatibilizer,which are also known to those of ordinary skill in the art. The rubbersare well known to the art and the literature and are commerciallyavailable from sources such as Bayer, Ameripol Synpol, Goodyear,Intertex, DuPont, and Zeon Chemicals. Most of the rubbers are describedin the Rubber Blue Book, published by Rubber World Magazine (2003)herein incorporated by reference.

Acrylic rubbers are preferred in many embodiments of the presentinvention. Generally two types of acrylic rubbers are prepared in theindustry. One type is derived from acrylic monomers and cure sitemonomers which provide sites for crosslinking. The second type ofacrylic rubber is derived from a combination of acrylate monomer(s),olefin monomer(s) such as ethylene, and one or more cure site monomers.Acrylic rubbers are typically formed using emulsion or solutionpolymerization, which is preferred for ethylene/acrylic type rubbers.Acrylate monomers include, but are not limited to, methyl acrylate,ethyl acrylate, propyl acrylate, and butyl acrylate. Acrylate monomersalso include alkoxy acrylates such as methoxy ethyl acrylate and ethoxyethyl acrylate, etc. Because acrylic rubbers have a saturated backbone,crosslinking is accomplished via incorporation of the copolymerizedreactive cure site monomers. Cure site monomers can vary, and caninclude a carboxylic acid, for example. Ethylene/acrylate type rubbersare generally cured with di- or polyfunctional amine, isocyanate, epoxy,or peroxide curing agents. Acrylic rubbers are commercially availablefrom various companies such as B.F. Goodrich of Charlotte, N.C. asHycar®, American Cyanimid as Cyanacryl®, and DuPont of Wilmington, Del.as Vamac® and Elf Atochem, of Exton, Pa. as Lotader® or Lotryl®.

The rubber component is present in an amount generally from about 40 toabout 80 or about 90 parts, desirably from about 45 or about 55 to about70 or about 75 parts by weight based on 100 parts by weight of therubber and thermoplastic matrix polymer in the thermoplastic elastomercomponent.

The thermoplastic elastomer component also includes a matrix polymerwhich is blended with the rubber before the rubber is cured ordynamically vulcanized. In a preferred embodiment, the matrix polymer isa polyolefin derived from substituted or unsubstituted olefin monomershaving from 2 to about 14 carbon atoms, with 2 to about 6 carbon atomspreferred. Likewise, polyamides, polyesters, or halogen-containingthermoplastics as described hereinabove can also be used as the matrixpolymer. The matrix polymer is chosen to be compatible with thethermoplastic polymer component. Compatibilizers are used in someembodiments when the matrix polymer is not otherwise compatible with thethermoplastic polymer component. Examples of suitable olefin monomersinclude, but are not limited to, ethylene, propylene, butene, pentene,hexene, heptene, and the like. The preferred olefins are ethylene andpropylene. Examples of various polyesters, polyamides, and halogenatedpolymers are described hereinabove with respect to the thermoplasticpolymer component and are hereby incorporated by reference.

Blends of matrix polymers are used in the thermoplastic elastomercomponent in some embodiments. In one embodiment the matrix polymer isdifferent than the thermoplastic polymer component. In anotherembodiment the matrix polymer is the same type of polymer as thethermoplastic polymer component, with the proviso that the numberaverage molecular weight can be either the same or different. In afurther embodiment the matrix polymer comprises a homopolymer in anamount generally greater than 70% by weight, desirably from about 80% toabout 100% by weight, and preferably from about 90% to about 100% byweight based on the total weight of the matrix polymer. Thus,homopolymer matrix polymers are preferred as opposed to the matrixpolymer comprising a greater amount of a copolymer.

One preferred embodiment utilizes a matrix polymer comprisingpolypropylene having a melt index of greater than 3 g or 3.5 g per 10minutes at 230° C. under a load of 2.16 kg according to ASTM D1238.

The matrix polymer component is present in the thermoplastic elastomerin a range generally from about 10 or about 20 to about 60 parts, anddesirably from about 25 or about 30 to about 45 or about 55 parts per100 parts by weight of the rubber and matrix polymer in thethermoplastic elastomer component. Matrix polymers for the thermoplasticelastomer component are commercially available from sources as listedabove with respect to the thermoplastic polymer component.

An important aspect of the present invention is to utilize at least onevulcanizing agent or crosslinker to crosslink the rubber component ofthe thermoplastic elastomer. The choice of a crosslinking agent dependsupon the rubber component. If the rubber component has no unsaturationor other functional group, then suitable crosslinking agents areperoxides. Specific examples of peroxide crosslinking agents include,but are not limited to, dibenzoyl peroxide, dicumyl peroxide,1,3-bis(t-butylperoxyisopropyl)benzene, di-t-butyl peroxide, dilauroylperoxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane,2,5-dimethyl-2,5-bis(t-butylperoxy)hexene-3 anddi(t-butylperoxy)perbenzoate, or a combination thereof. Peroxides may beused with crosslinker coagents to improve the crosslinking efficiency.The common coagents used with peroxides have two or more unsaturatedgroups, or labile hydrogen groups. Examples are triallyl cyanuarate;triallyl isocyanuarate; di, tri and tetra methyacrylates and acrylatessuch as those available from ATOChem under the trade name Sartomer®;liquid butadiene; and the like. Siloxane is an example of the lattertype coagent. For elastomers with unsaturation, the peroxides describedabove are utilized in one embodiment. In addition to the peroxides,alternative curatives include sulfur based curatives, dimethylol phenol(which is halogenated or non-halogenated) with Lewis acids, or siliconeprepolymers with two or more SiH groups. The latter uses small amount ofplatinum or other metal complexes as a catalyst. If the elastomer has afunctional group, such as an acid, amine, isocyanate, epoxy or the like,curatives include a bifunctional or polyfunctional compound, or apolymer that will react with that particular group as a curative.Non-limiting specific examples of such crosslinking agents include metaloxides such as magnesium oxide, isocyanate prepolymers such as Mondur®available from Bayer of Baytown, Tex., and neopentyl(diallyl)oxytri(N-ethylenediamino)ethyl titanate. Thus, for an acidfunctional rubber or elastomer, curatives include a compound, aprepolymer, or polymer containing an epoxy, alcohol, isocyanate, amineand the like functionalities that will react with the acid group.

The amount of crosslinking agent will depend upon the functionality andmolecular weight of the crosslinking agent and desired level ofcrosslinking. That said, the amount of crosslinking or vulcanizing agentis generally small and ranges from about 0.5 to about 15 parts byweight, desirably from about 0.75 to about 10 parts by weight, andpreferably from about 1 to about 6 parts by weight, based on 100 partsby weight of the rubber component.

In addition to the above-identified components, the thermoplasticelastomer component of the present invention optionally include variousadditives, fillers, lubricants, stabilizers, accelerators, processingaids, compatibilizers, flame retardants, dispersing aids, colorants, andthe like, which are utilized in conventional amounts. Non-limitingexamples of fillers include both organic and inorganic fillers such assilica, organically modified silica, talc, clay, and fibers such as woodfibers or glass fibers. Non-limiting examples of pigments or colorantsinclude carbon black and titanium dioxide.

The thermoplastic elastomer composition is formed by combining, i.e.,mixing, blending or the like, predetermined amounts of the rubbercomponent, matrix polymer component, crosslinking agent, and any otheroptional components together and then dynamically vulcanizing thecomposition. Dynamic vulcanization is typically characterized as aprocess, well known to those of ordinary skill in the art, wherein atleast one rubber is crosslinked in the presence of at least onenon-vulcanizing polymer, for example a thermoplastic matrix polymer,while the blend is mixed, preferably at an elevated temperature whichpromotes said crosslinking.

Any melt mixing, masticating, or kneading apparatuses or methods asknown in the art are utilized to prepare the thermoplastic elastomercomposition, including apparatuses such as, but not limited to, rollmills, Banbury mixers, Brabender mixers, and extruders, with twin screwextruders being preferred. The temperature for dynamic vulcanization toform the crosslinked elastomer will depend upon the melting point of thethermoplastic matrix. Usually the temperature used is about 10° C. ormore higher than the matrix melt temperature. Also, desired rate ofreaction and crosslinking agent type also dictate the temperature used.The temperature for dynamic vulcanization to form the elastomer rangesgenerally from about 100° C. to about 280° C. The dynamic vulcanizationof the uncured rubber is performed for a predetermined length of timeuntil the desired degree of crosslinking is obtained, and rangesgenerally from about 0.1 to about 10 minutes, and preferably from about1 to about 3 minutes. The crosslinking of the rubber is dependent onmany factors including the composition temperature, amount ofcrosslinking agent present, and shear rate, etc.

In a preferred embodiment, the thermoplastic elastomer composition isprepared by melt blending the matrix polymer and the rubber component,fillers, appropriate additives and extender oil in a first step. In asecond step, the crosslinking agent is added to the melt mixed blend andmixing is continued until the crosslinking reaction is completed to thedesired degree. Afterwards, any additional components are added and thethermoplastic elastomer is mixed for a further period of time, such asabout 1 to about 5 minutes.

The melt mixed, dynamically vulcanized thermoplastic elastomercomposition is formed into a desired end product such as a pellet, chip,flake, or the like.

The thermoplastic elastomer component thus includes the cured rubbercomponent and the thermoplastic matrix polymer. The thermoplasticelastomer is preferably in the form of a mixture with the rubbercomponent in the form of dispersed micron sized rubber particles withinthe continuous phase matrix polymer. The cured rubber componentparticles have an average particle size generally from about 0.005 toabout 25 microns, desirably from about 0.05 to about 15 microns, andpreferably from about 0.1 to about 10 microns.

Once dynamically vulcanized, the thermoplastic elastomer composition isblended with the thermoplastic polymer component. That is, the toughenedpolymers of the present invention are a blend of the crystalline orsemi-crystalline thermoplastic polymer component and the crosslinkedthermoplastic elastomer component comprising the crosslinked rubbercomponent and the matrix polymer. Preferably the thermoplastic elastomercomponent is compatible with the thermoplastic component. Otherwise, acompatabilizer is used to provide compatibility. Such compatibilizersare known to those of ordinary skill in the art. The blend is preparedaccording to conventional compounding methods by combining thecomponents, and then preferably melt processing at a predeterminedtemperature in a suitable apparatus. The blend is melt processed at atemperature above the melting point of the thermoplastic polymercomponent, desirably about 10° C. to about 50° C. above the meltingpoint, and preferably from about 20 to about 30° C. above melting pointof the thermoplastic component, but below any decomposition temperatureof any of the components.

As the amounts of both the matrix polymer and thermoplastic polymercomponent can each vary by weight in relation to the rubber component,one characterization of the invention defines the rubber component inrelation to 100 total parts by weight of any thermoplastic utilized,i.e., both the matrix polymer and the thermoplastic polymer component.The toughened polymer composition comprises the rubber component of thethermoplastic elastomer component in a range generally from about 2 toabout 60 parts, desirably from about 5 or about 10 to about 50 parts,and preferably from about 8 or about 15, or about 18 to about 42 orabout 45 parts per 100 total parts by weight of the matrix polymer andthermoplastic polymer component.

The toughened polymer compositions of the present invention utilizerelatively low amounts of extender or rubber processing oil known to theliterature and to the art. The amount of oil in the toughened polymercompositions of the present invention is less than about 35 parts,desirably less than about 25 parts, and preferably less than about 20 orabout 15 parts per 100 total parts by weight of the rubber component.

Additionally, the toughened polymer compositions are substantially freeof plasticizers. The amount of plasticizer in the composition isgenerally less than about 10 parts, desirably less than about 5 partsand preferably less than about 3 parts or nil, by weight per 100 totalparts by weight of thermoplastic polymer and matrix polymer.

In addition to the above-identified components, the toughened polymerblend of the present invention optionally includes various additives,fillers, lubricants, stabilizers, processing aids, antidegredants,waxes, fibers such as glass, wood, or cellulose fibers, clay, silica,compatibilizers, flame retardants, dispersing aids, colorants, and thelike, which are utilized in conventional amounts as known to the art andto the literature. As with the formation of the thermoplastic elastomercomposition, the toughened polymer compositions are melt processedutilizing standard equipment known to the art such as roll mills,Banbury mixers such as Brabender mixers, and extruders, with twin screwextruders being preferred.

After the components of the toughened polymer compositions have beenmixed or blended, and preferably melt mixed, the blend is then processedinto a desired form utilizing equipment known in the art such aspelletizers to form particles such as pellets, chips, flakes, spheres orthe like. The toughened polymer composition can be subsequentlyreprocessed utilizing any known polymer processing equipment to formsuitable articles as the elastomer morphology is not altered by furtherprocessing thus retaining desired properties. In a preferred embodiment,the toughened polymer composition is prepared in an extruder,subsequently pelletized and dried.

The toughened polymer compositions unexpectedly have a high Rockwell “R”hardness as well as the relatively high impact resistance when comparedto the thermoplastic component alone. The toughened polymer compositionsare formulated to have a greater hardness while at least maintainingimpact properties, or greater impact resistance while at leastmaintaining hardness, and preferably to have both greater hardness andimpact resistance, when compared to the thermoplastic polymer componentblended with an uncured thermoplastic elastomer component. In apreferred embodiment, the toughened polymer compositions have a notchedizod impact at minus 40° C. of at least 1.0 ft.-lb/in and preferably atleast 1.3 ft.-lb/in as measured by ASTM D256. It has been found thatwhen polyesters are utilized as the thermoplastic polymer component aswell as the matrix polymer at a concentration of ≦85 parts by 100 partsby weight total polyester and rubber, notched izod impact values at −20°C. of at least 3.0 ft.-lb/in, and preferably at least 3.75 ft.-lb/in areobtained as measured according to ASTM D256. Likewise, when thepolyester concentration is ≦75 parts per 100 total parts by weightpolyester and rubber, notched izod impact at −20° C. of at least 4.75ft.-lb/in. and preferably at least 5.0 ft.-lb/in are obtained asmeasured according to ASTM D256. It has been found when polyamides areutilized for the thermoplastic polymer component as well as matrixpolymer at a concentration of ≦85 parts by 100 parts by weight polyamideand rubber, notched izod impact values at −20° C. of at least 1ft.-lb/in, and preferably at least 2 ft.-lb/in are obtained as measuredby ASTM D256. Likewise, when the polyamide concentration is ≦75 partsper 100 total parts by weight polyamide and rubber, notched izod impactat −20° C. of at least 3.25 ft.-lb/in and preferably at least 4.0ft.-lb/in are obtained as measured by ASTM D256.

The toughened polymer compositions are useful in any application whereina toughened polymeric product or article is desired. The toughenedpolymer compositions are utilized in numerous processes known in the artincluding, but not limited to, extrusion, injection molding, blowmolding, compression molding, thermoforming, and rotational molding.

The toughened polymer compositions are formed into generally any plasticgood or item including, but not limited to, display racks, carts such asfood carts, medical carts and farm carts, instrument housings,watercraft such as kayaks, boats and canoes, items for agriculturalapplications such as corn picker points, truck boxes, beveragecontainers, planter pots, newspaper cabinets, tables, coolers,furniture, storage trays, tanks such as fuel tanks and water tanks,playground equipment and bed liners.

It has been unexpectedly found that the toughened polymer compositionsof the present invention are particularly suitable for producingrotationally molded articles. The toughened polymer compositions whenrotationally molded, produce parts having high surface quality withexcellent hardness as well as impact strength. During rotationalmolding, polymeric compositions are subjected to relatively hightemperatures for extended periods of time as compared to injectionmolding. It is known to art that uncured rubber-containing compositionsare not suitable for rotational molding as the rubber is not stableduring the extended period of molding time. For example, impactpolystyrene and ABS produce rotationally molded articles having poorsurface quality due to the instability and degredation of therubber-like components of the compositions. Moreover, heretofore uniformmelt flow could not be obtained, thus producing rotationally moldedarticles with irregular, and rough surfaces, etc. It has been found thatthe vulcanized thermoplastic elastomer component of the toughenedpolymer blend having the defined particle size allows rotationallymolded articles to be produced having excellent surface quality.

Rotational molding devices are well known to those of ordinary skill inthe art and are commercially available from Ferry Industries, Alan YorkeEngineering LTD, and Caccia Engineering S.p.A. Generally any type ofrotational molding apparatus can be utilized, such as turret machines,shuttle machines, hybrid shuttle/rocking oven machines, swing machines,rock and roll machines, clamshell machines, vertical wheel machines, andthe like. Rotational molding devices generally include aloading/unloading station, an oven station and a cool down station.

Rotational molding of the toughened polymer compositions of the presentinvention is accomplished in one embodiment as follows. A predeterminedamount of the toughened polymer composition and any optional additivessuch as, but not limited to, colorants, stabilizers, flame retardants,etc. are added to a mold that is in the shape of the article to bemolded. Preferably the toughened polymer is added in the form of apowder or other small particle. The mold is also preferably vented toprevent flash at the parting line as well as warping. The mold issubsequently closed and transferred to the oven section or heating zonewherein the mold is rotated at an elevated temperature above the meltingpoint of the toughened polymer composition and generally at atemperature from about 500° F. (260° C.) to about 700° F. (371° C.).

In a preferred embodiment, the mold is rotated about a horizontal and avertical axis simultaneously. Rotation speed for each axis,independently ranges from about 1 to about 25 or 50 rpm, and generallyfrom about 2 to about 20 rpm. For example, in one embodiment the moldcan be rotated at 15 rpm about a horizontal axis and about 3 rpm in thevertical axis. The mold is maintained in the oven section for apredetermined period of time such as generally from about 8 minutes toabout 25 minutes or more, and preferably from about 10 to about 15minutes.

Afterwards, the mold containing the toughened polymer composition ispreferably moved to a cooling station and cooled to ambient temperature.Means for cooling the mold include the use of one or more fans, watersprayers or the like. The article formed in the mold from the toughenedpolymer composition is removed from the mold after cooling.

Toughened polymer articles formed by rotational molding can be formed inone piece and are virtually stress free. Uniform wall thicknesses can beobtained with substantially no thinning at the extremities. Numerousdifferent articles are formed ranging from small and intricate items tolarge and complex items, some of which are noted above. Articles arealso formed having metal inserts and/or double walled moldings.

The present invention will be better understood by reference to thefollowing examples which serve to describe, but not to limit, thepresent invention.

EXAMPLES

Examples of the toughened polymer compositions of the present inventionincluding the thermoplastic polymer component and thermoplasticelastomer component were prepared as described hereinbelow. Thetoughened polymer compositions were compared to the control formulationsdescribed below. The results show that the toughened polymercompositions exhibit improved impact resistance and/or hardness whencompared to control formulations.

Example 1

A thermoplastic elastomer component was prepared in a first step,wherein a rubber component was blended with a matrix polymer in amountsas listed in Table I and subsequently cured. A control formulation wasalso prepared including a rubber component and a matrix polymer. Thecontrol formulation was not cured during melt blending as it lacked acrosslinking agent. The thermoplastic elastomer component and controlformulation were each melt blended at a temperature of 200° C. for about30 seconds in a twin screw extruder at 200 RPM. A peroxide curative,α,α′-bis(tert-butylperoxy)-diisopropylbenzene, was added to thethermoplastic elastomer component and mixed for about 30–40 secondsuntil the reaction was completed. The control was mixed for the samelength of time, but no curative was utilized. The thermoplasticelastomer component and control were each then pelletized. Afterwards,the thermoplastic elastomer component and control formulation wereindividually blended with a thermoplastic polymer component in theamounts shown in Table IA. The blends were melt mixed at 210° C. forabout 1 to 2 minutes in a twin screw extruder at 200 RPM andsubsequently pelletized. Test samples were produced by injection moldingat about 220° C. The various compositions exhibited the propertieslisted in the tables.

The results listed in Table IA show that the toughened polymercompositions of the present invention exhibit higher tensile strength,greater hardness, and higher notched izod impact value at both room andlow temperatures when compared to the control formulations at differentthermoplastic polymer component levels.

TABLE I Thermoplastic Elastomer Composition 1 Control 1 EPDM Rubber¹(rubber component) 100 100 Polypropylene² (matrix polymer) 90 90Polyethylene³ (matrix polymer) 6 6 Calcium Carbonate 10 10 LiquidPolybutadiene⁴ 5 0.0 Peroxide⁵ (crosslinking agent) 1.10 0.0 UVStabilizer⁶ 1.80 1.80 Calcium Stearate 0.55 0.55 Polyethylene Wax 1.251.25 Processing Oil⁷ 10.0 10.0 TOTAL (parts by weight) 225.70 219.60¹Royalene 525 (Uniroyal) ²Fortilene 9000 (Solvay Polymers) ³HDPE 6.5MIT60-500 (Solvay Polymers) ⁴Ricon (Ricon Polymers) ⁵Vulcup 40 KE (GEOSpecialty Chemicals) ⁶50/50 Irganox 1010 and Irgafos 168 (Ciba Geigy)⁷Semtol (Witco)

TABLE IA Control Control Control Example 1 Ex. 1 Example 2 Ex. 2 Example3 Ex. 3 Thermoplastic Elastomer 225.70 — 225.70 — 225.70 — Composition(parts by weight) (Table I) Control 1 (parts by weight) (Table I) —219.60 — 219.60 — 219.60 Polypropylene⁸ (thermoplastic 150 150 250 250350 350 polymer component) (parts by weight) TOTAL (parts by weight)375.70 369.60 475.70 469.60 575.70 569.60 Rubber component parts per 10040.65 40.65 28.90 28.90 22.42 22.42 parts by weight matrix polymer andthermoplastic polymer component CROSSLINKED RUBBER, Wt. % 26.617 27.05621.022 21.295 17.370 17.556 POLYOLEFIN, Wt. % 65.480 66.558 72.73573.680 77.471 78.301 Oil, Wt. % 2.662 2.706 2.102 2.129 1.737 1.756OTHERS, Wt. % 5.243 3.680 4.141 2.896 3.422 2.388 TOTAL WEIGHT % 100.0100.0 100.0 100.0 100.0 100.0 Specific Gravity (ASTM D792) 0.91 0.920.90 0.91 0.91 0.91 Hardness, Shore D(Inst/10 Sec.) 66/60 65/59 72/6868/60 75/71 71/65 (ASTM D2240) Hardness, Rockwell “R” (ASTM 33.7 — 49.3— 54.2 — D785) Tensile Strength(2″/min), Psi (ASTM 3460 2670 3640 30803460 3450 D638) Elongation @ Break(2″/min), % 570 610 500 680 510 490(ASTM D638) Low Temperature Break, ° C. (ASTM ~−60 −50 −47 −50 −42 −40D746) MI, g/10 min (230° C./2.16 kg) (ASTM 0.77 1.30 1.51 2.25 2.12 2.53D1238) MI, g/10 min (230° C./5.0 kg) (ASTM 4.39 5.66 7.60 10.50 10.6512.00 D1238) Unnotched Izod Impact, Ft-lb/in (@ No break No break No Nobreak No break 18.2 ~23° C.) (ASTM D256) break Unnotched Izod Impact,Ft-lb/in (@ No break 21.2 No 13.1 No break 10.9 ~−40° C.) (ASTM D256)break Notched Izod Impact, Ft-lb/in (@ No break 14.7 No 3.1 No break 2.6~23° C.) (ASTM D256) break Notched Izod Impact, Ft-lb/in (@ ~−40° C.)2.4 0.9 1.3 0.6 1.4 0.4 (ASTM D256) ⁸Fortilene 9300 (Solvay Polymers)

Table II illustrates toughened polymer compositions utilizing variousamounts of extender oil and the thermoplastic elastomer component as setforth in Table I. The toughened polymer blend was prepared in the samemanner as set forth above. Table II illustrates that generally lowamounts of oil do not adversely affect the properties of the toughenedpolymer compositions.

TABLE II Example Example Example Example Example Example Example ExampleExample Example 4 5 6 7 8 9 10 11 12 13 Oil (parts by weight) 0.0005.255 10.511 15.766 21.022 0.000 3.996 7.991 11.987 15.982 ThermoplasticElastomer 225.70 225.70 225.70 225.70 225.70 225.70 225.70 225.70 225.70225.70 Composition (parts by weight) (Table I) Polypropylene⁸(thermoplastic 250 250 250 250 250 400 400 400 400 400 polymercomponent) (parts by weight) TOTAL (parts by weight) 475.70 480.95486.21 491.46 496.72 625.70 629.69 633.69 637.68 641.68 Rubber componentparts per 28.90 28.90 28.90 28.90 28.90 20.16 20.16 20.16 20.16 20.16100 parts by weight matrix polymer and thermoplastic polymer componentCROSSLINKED 21.022 20.792 20.567 20.347 20.130 15.980 15.881 15.78015.682 15.584 RUBBER, Wt. % POLYOLEFIN, Wt. % 72.735 71.939 71.16370.401 69.656 79.271 78.768 78.272 77.781 77.297 Oil, Wt. % 2.102 3.1724.219 5.243 6.245 1.598 2.223 2.839 3.448 4.049 OTHERS, Wt. % 4.1414.096 4.052 4.008 3.966 3.148 3.128 3.109 3.089 3.070 TOTAL WEIGHT %100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 SpecificGravity 0.90 0.92 0.91 0.90 0.90 0.91 0.91 0.91 0.91 0.91 (ASTM D792)Hardness, Shore D 72/68 68/64 65/60 66/60 64/59 74/70 69/63 69/63 69/6369/63 (Inst/10 Sec.) (ASTM D2240) Hardness, Rockwell ″R″ 49.3 — — — —62.0 — — — — (ASTM D785) Tensile Strength (2″/min), Psi 3640 2520 29102940 2910 3720 3210 3130 3160 3260 (ASTM D638) Elongation @ Break 500570 620 580 600 540 630 640 610 520 (2″/min), % (ASTM D638) LowTemperature Break, ° C. −47 ~−60 −56 −56 −54 −39 −54 −56 −52 −40 (ASTMD746) MI, g/10 min (230° C./2.16 1.51 1.90 1.30 1.50 1.35 2.63 2.07 2.362.47 2.30 kg) (ASTM D1238) MI, g/10 min (230° C./5.0 7.60 9.30 6.52 7.336.95 12.75 11.10 11.60 11.40 10.80 kg) (ASTM D 1238) Unnotched IzodImpact, No break No break No break No break No break No break No breakNo break No break No break Ft.-lb/in (@ ~23° C.) (ASTM D256) UnnotchedIzod Impact, No break No break No break No break No break 19.8 No breakNo break No break No break Ft.-lb/in (@ ~−40° C.) (ASTM D256) NotchedIzod Impact, Ft.-lb/in No break No break No break No break No break 4.23.3 4.0 4.0 3.2 (@~23° C.) (ASTM D256) Notched Izod Impact, Ft.-lb/in1.3 1.300 1.500 1.500 1.300 1.200 1.200 1.300 1.000 1.000 (@~−40° C.)(ASTM D256) ⁸Fortilene 9300 (Solvay Polymers)

Example 2

Polyester-based toughened polymer compositions were prepared in afurther example. A thermoplastic elastomer component was prepared in afirst step, wherein an acrylic rubber component was blended with apolyester matrix polymer in amounts as listed in Table III andsubsequently cured. A control formulation was also prepared which wasnot cured during melt blending as it lacked a crosslinking agent. Thethermoplastic elastomer component and control formulation were each meltblended for about three minutes in a banbury after the stock temperaturereached about 230° C. The control compound was removed and formed into asheet on a roll mill and cooled. The noted crosslinking agents wereadded to the respective thermoplastic elastomer component (TPV) afterthe first melt mixing step, and mixing was continued for three minutesafter maximum torque was reached. Care was taken to maintain atemperature below about 235° C. utilizing cooling water through theequipment and/or reduction in mixing speed. The thermoplastic elastomercomponents were each removed from the banbury and formed into a sheet bypassing through a roll mill. The control formulation and thermoplasticelastomer component were each melt mixed with various amounts ofpolyester thermoplastic polymer components in the amounts shown in TableIIIA. The toughened polymer composition blends were melt mixed in abanbury at about 230° C. for three minutes for a first mixing, and thenfor about a two minute remixing period. The compositions were granulatedand injection molded to produce test samples. The compositions exhibitedthe properties listed in Table IIIA.

The results listed in Table IIIA show that the toughened polymercompositions of the present invention exhibit higher hardness, andhigher notched izod impact values when compared to the controlformulations at different thermoplastic elastomer component levels.

TABLE III Control TPV 1 TPV 2 TPV 3 Polyester¹ (matrix polymer) 40.040.0 40.0 40.0 Acrylic Rubber² 60.0 60.0 60.0 60.0 (rubber component)Neopentyl(diallyl)oxytri(N- — 0.9 1.2 — ethylenediamino)ethyl titanate³(crosslinking agent) Magnesium Oxide⁴ (crosslinking — — — 3.0 agent)Stabilizer⁵ 0.6 0.6 0.6 0.6 Stabilizer⁶ 0.2 0.2 0.2 0.2 Calcium Stearate0.3 0.3 0.3 0.3 Magnesium Stearate⁷ 0.3 0.3 0.3 0.3 TOTAL (parts byweight) 101.40 102.30 102.60 104.40 ¹Valox 315 (polybutyleneterephthlate) (General Electric) ²Vamac G (DuPont) ³Kenreact Lica 44(Kenrich Petrochemicals) ⁴Maglite D (C. P. Hall) ⁵Ethanox 330(Albermarle Corp.) ⁶DSTDP (Cytec Industries) ⁷(Crompton)

TABLE IIIA Control Control Control Exam- Exam- Exam- Exam- Exam- Exam-Exam- Exam- Exam- Ex. 1 Ex, 2 Ex. 3 ple 1 ple 2 ple 3 ple 4 ple 5 ple 6ple 7 ple 8 ple 9 TPV 1(parts by weight) (Table III) — — — 102.30 102.30102.30 — — — — — — TPV 2 (parts by weight) (Table III) — — — — — —102.60 102.60 102.60 — — — TPV 3 (parts by weight) (Table III) — — — — —— — — — 104.40 104.40 104.40 Control (parts by weight) 101.4 101.4 101.4— — — — — — — — (Table III) Polyesters (thermoplastic polymer 300 200140 300 200 140 300 200 140 300 200 140 component) (parts by weight)TOTAL (parts by weight) 401.40 301.40 241.40 402.30 302.30 242.30 402.60302.60 242.60 404.40 304.40 244.40 RUBBER (Crosslinked or 14.95 19.9024.86 14.91 19.85 24.76 14.90 19.83 24.73 14.84 19.71 24.55uncrosslinked), Wt % POLYESTER (PBT), Wt % 84.70 79.64 74.56 84.52 79.3974.29 84.45 79.31 74.20 84.07 78.84 73.65 OTHER, Wt. % 0.35 0.46 0.580.57 0.76 0.95 0.65 0.86 1.07 1.09 1.45 1.80 TOTAL WEIGHT % 100.0 100.0100.0 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00PROPERTIES Specific Gravity (ASTM D792) 1.26 1.24 1.23 1.25 1.24 1.221.26 1.24 1.23 1.26 1.24 1.23 Hardness, Shore D(Inst/10 Sec.) 73 70 7075 73 70 76 75 71 73 73 68 (ASTM 2240) Tensile Strength @yield (2″/min),5420 5110 4740 5120 4710 4120 4730 4160 3640 5220 4490 3740 Psi (ASTMD638) Elongation @ yield (2″/min), % 5 5 6 6 11 15 5 5 5 4 4 5 (ASTMD638) Tensile Strength @ break (2″/min), 3820 3550 2670 5020 4570 45505920 5320 5060 5050 4920 5130 Psi (ASTM D638) Elongation @ Break(2″/min), % 72 150 140 220 300 310 360 370 380 280 350 360 (ASTM D638)Izod Impact, Ft.-lb/in (@ ~25° C.) 10.7 13.5 16.4 12.2 16.7 24.5 12.115.3 22.1 12.6 18.5 20.6 (ASTM D256) Notched Izod Impact, Ft.-lb/in 2.783.88 4.56 3.96 4.37 5.62 4.46 4.46 5.19 3.81 4.42 5.38 (@ ~20° C.) (ASTMD256) ⁸Valox 315 (General Electric)

Example 3

Polyamide-based toughened polymer compositions were prepared in afurther example. A thermoplastic elastomer component was prepared in afirst step, wherein an acrylic rubber component was blended with apolyamide matrix polymer in amounts as listed in Table IV andsubsequently cured. A control formulation was also prepared which wasnot cured during melt blending as it lacked a crosslinking agent. Athermoplastic elastomer component and control formulation were each meltblended for about three minutes in a banbury after the stock temperaturereached about 230° C. The control compound was removed and formed into asheet on a roll mill and cooled. The noted crosslinking agents wereadded to the thermoplastic elastomer component after the first meltmixing step, and mixing was continued for three minutes after maximumtorque was reached. Care was taken to maintain a temperature below about235° C. utilizing cooling water through the equipment and/or reductionin mixing speed. The thermoplastic elastomer components were eachremoved from the banbury and formed into a sheet by passing through aroll mill. The control formulation and thermoplastic elastomer componentwere each melt mixed with various amounts of polyamide thermoplasticpolymer components in the amounts shown in Table IVA. The toughenedpolymer composition blends were melt mixed in a banbury at about 230° C.for three minutes for a first mixing, and then about a two minuteremixing period. The compositions were granulated and injection moldedto produce test samples.

The results listed in Table IVA show that the toughened polymercompositions of the present invention exhibit similar hardness, andhigher notched izod impact values when compared to the controlledformulations at different thermoplastic elastomer component levels.

TABLE IV Control TPV 1 TPV 2 Polyamide¹ (matrix polymer) 40.0 40.0 40.0Acrylic Rubber² (rubber component) 60.0 60.0 60.0Neopentyl(diallyl)oxytri(N- — 1.2 1.2 ethylenediamino)ethyl titanate³(crosslinking agent) Magnesium Oxide⁴ (crosslinking agent) — — 3.0Stabilizer⁵ 0.6 0.6 0.6 Stabilizer⁶ 0.2 0.2 0.2 Calcium Stearate 0.3 0.30.3 Magnesium Stearate⁷ 0.3 0.3 0.3 TOTAL (parts by weight) 101.40102.60 104.40 ¹Ultramid 8202 Nylon-6 (BASF) ²Vamac G (DuPont) ³KenreactLica 44 (Kenrich Petrochemicals) ⁴Maglite D (C. P. Hall) ⁵Ethanox 330(Albermarle Corp.) ⁶DSTDP (Cytec Industries) ⁷(Crompton)

TABLE IVA Control Control Control Exam- Ex. 1 Ex. 2 Ex. 3 Example 1Example 2 Example 3 Example 4 Example 5 ple 6 TPV 1 (parts by weight)(Table IV) — — — 102.60 102.60 102.60 — — — TPV 2 (parts by weight)(Table IV) — — — — — — 104.40 104.40 104.40 Control 1 (parts by weight)(Table IV) 101.4 101.4 101.4 — — — — — — polyamide (thermoplasticpolymer 300 200 140 300 200 140 300 200 140 component) (parts by weight)TOTAL (parts by weight) 401.40 301.40 241.40 402.60 302.60 242.60 404.40304.40 244.40 RUBBER (Crosslinked or 14.95 19.90 24.86 14.91 19.85 24.7614.84 19.71 24.55 uncrosslinked) POLYAMIDE (Nylon-6) 84.70 79.64 74.5684.52 79.39 74.29 84.07 78.84 73.65 OTHER, Wt. % 0.35 0.46 0.58 0.570.76 0.95 1.09 1.45 1.80 TOTAL WEIGHT % 100.0 100.0 100.0 100.00 100.00100.00 100.00 100.00 100.00 PROPERTIES Specific Gravity (ASTM D792) 1.111.10 1.10 1.11 1.11 1.11 1.11 1.13 1.10 Hardness, Shore D(Inst/10 Sec.)79 79 76 79 75 73 78 75 72 (ASTM 2240) Tensile Strength @yield (2″/min),Psi 6400 5700 5160 5800 5200 4600 6200 5800 4760 (ASTM D638) Elongation@ yield (2″/min), % 10 10 12 20 25 30 10 6 10 (ASTM D638) TensileStrength @ break (2″/min) 8200 6100 6820 7000 6600 6180 7000 7700 6400Psi (ASTM D638) Elongation @ Break (2″/min), % 260 200 270 280 290 310320 360 340 (ASTM D638) Izod Impact, Ft.-lb/in (@ ~25° C.) 5.3 9.9 12.69.4 14.0 19.8 10.8 17.2 20.5 (ASTM D256) Notched Izod Impact, Ft.-lb/in(@ 0.33 2.74 3.03 2.25 4.10 4.78 2.04 3.20 3.33 ~20° C.) (ASTM D256)⁸Ultramid 8202 (BASF)

Tables V and VA illustrate additional toughened polymer compositions ofthe present invention as compared to a control formulation. In thisexperiment, two different rubber components and a filler were used inthe same thermoplastic elastomer composition to show that rubber blendsform effective toughened polymer compositions. The thermoplasticelastomer composition, controls, and the toughened blends were preparedin the same manner as set forth above.

The results listed in Table VA show that blends of more than one rubberand more than one polyolefin are effectively utilized to form atoughened polymer composition having desired properties. The toughenedpolymer compositions of Examples 14 and 15 exhibit higher tensilestrength, higher hardness, and both unnotched izod impact and notchedizod impact at the tested temperature ranges, when compared to exampleformulations with rubber components which were not crosslinked.

TABLE V Thermoplastic Elastomer Composition 2 Control 2 EPDM Rubber¹(rubber component) 90 90 EPDM Rubber⁹ (rubber component) 10 10Polypropylene² (matrix polymer) 90 90 Polyethylene³ (matrix polymer) 6 6Calcium Carbonate Filler 40 40 Liquid Polybutadiene⁴ 5 0.0 Peroxide⁵(crosslinking agent) 1.10 0.0 UV Stabilizer⁶ 1.80 1.80 Calcium Stearate0.55 0.55 Polyethylene Wax 1.25 1.25 Processing Oil⁷ 10.000 10.000 TOTAL(parts by weight) 255.70 249.60 ⁹Royaltuf 485 (Uniroyal)

TABLE VA Example Control Example Control 14 Ex. 14 15 Ex. 15 Control 2 —249.60 — 249.60 Thermoplastic Elastomer 255.70 — 255.70 — Composition(parts by weight) Polypropylene⁸ 150 150 250 250 (thermoplastic polymercomponent) (parts by weight) TOTAL WEIGHT 405.70 399.60 505.70 499.60(parts by weight) Rubber component 40.65 40.65 28.90 28.90 parts byweight per 100 parts matrix polymer and thermoplastic polymer componentCROSSLINKED 24.649 25.025 19.775 20.016 RUBBER, Wt. % POLYOLEFIN, Wt. %60.635 61.562 68.420 69.255 Oil, Wt. % 2.465 2.503 1.977 2.002 OTHERS,Wt. % 12.250 10.911 9.828 8.727 TOTAL WEIGHT % 100.0 100.0 100.0 100.0pecific Gravity 0.99 0.98 0.93 0.91 (ASTM D792) Hardness, Shore D 67/6266/58 72/67 66/56 (Inst/10 Sec.) (ASTM D2240) Hardness, Rockwell 37.5 —46.2 — “R” (ASTM D785) Tensile Strength 3620 2190 3830 2430 (20″/min),Psi (ASTM D638) Elongation @ Break 550 600 530 680 (20″/min), % (ASTMD638) Low Temperature ~−60 ~−60 −50 ~−60 Break, ° C. (ASTM D746) MI,g/10 min 0.72 0.94 1.28 1.65 (230° C./2.16 kg) (ASTM D 1238) MI, g/10min 4.18 4.68 6.58 7.93 (230° C./5.0 kg) (ASTM D 1238) Unnotched Izod NoNo No No Impact, Ft.-lb/in break break break break (@ ~23° C.) (ASTMD256) Unnotched Izod 22.9 15.5 24.7 19.7 Impact, Ft.-lb/in (@ ~−40° C.)(ASTM D256) Notched Izod No 12.0 No 13.4 Impact, Ft.-lb/in break break(@ ~23° C.) (ASTM D256) Notched Izod 1.7 1.4 1.3 1.2 Impact, Ft.-lb/in(@ ~−40° C.) (ASTM D256) ⁸Fortilene 9300 (Solvay Polymers)

In accordance with the patent statutes, the best mode and preferredembodiment have been set forth; the scope of the invention is notlimited thereto, but rather by the scope of the attached claims.

1. A process for preparing a toughened polymer composition, comprisingthe steps of: combining a rubber component and a matrix polymer, saidmatrix polymer comprising a polyester or polyamide; mixing andcrosslinking the rubber component in the presence of the matrix polymerwith a crosslinking agent at a temperature above the melting point ofthe matrix polymer to form a thermoplastic elastomer component; andblending the thermoplastic elastomer component with a thermoplasticpolymer component comprising a polyester or polyamide to form thetoughened polymer composition, wherein the toughened polymer compositionoptionally includes a compatibilizer.
 2. A process according to claim 1,wherein the rubber component of the thermoplastic elastomer component ispresent in an amount from about 2 to about 60 parts by weight per 100parts by weight of the matrix polymer of the thermoplastic elastomercomponent and the thermoplastic polymer component.
 3. A processaccording to claim 2, wherein the thermoplastic polymer component andmatrix polymer of the thermoplastic elastomer component are,independently, a polyamide derived from polycondensation of a diaminehaving from 4 to 12 carbon atoms and a dibasic acid having from 4 to 12carbon atoms; or derived from selfpolycondensation of an amino acid; orderived from polymerization of a lactam; or a polyester derived from adicarboxylic acid having from about 2 to about 16 carbon atoms and adiol or diol derivative having from about 2 to about 16 carbon atoms; orderived from selfcondensation of a hydroxy carboxylic acid; or derivedfrom ring opening polymerization of a lactone, wherein the rubbercomponent of the thermoplastic elastomer component is derived from atleast two different alpha olefin monomers, or is styrene butadienerubber, hydrogenated styrene butadiene rubber, butyl rubber,butyl-paramethyl styrene copolymer or derivatives thereof, styrenicblock copolymer, acrylic rubber, nitrile rubber, hydrogenated nitrilerubber, or ethylene methacrylate terpolymer rubber, or any combinationthereof.
 4. A process according to claim 3, wherein the crosslinkedrubber component of the thermoplastic elastomer component has an averageparticle size of about 0.005 to about 25 microns, and wherein thethermoplastic elastomer component and thermoplastic polymer componentare melt blended.
 5. A process according to claim 1, wherein saidthermoplastic polymer component is nylon-4, nylon-4,6,polyhexamethyleneadipamide (nylon-6,6), polycaprolactam (nylon-6), nylon6,9, polyhexamethylenesebacamide (nylon-6,10), nylon-11, nylon-12 orcopolymers thereof; or polyethylene terephthalate, polybutyleneterephthalate, polyethylene isophthalate, or a block polyetherester, ora combination thereof; and wherein said rubber component of thethermoplastic elastomer component is an acrylic rubber.
 6. A processaccording to claim 5, wherein the rubber component of the thermoplasticelastomer component is present in an amount from about 40 to about 90parts by weight per 100 parts by weight of the rubber component and thematrix polymer of the thermoplastic elastomer component, and wherein therubber component of the thermoplastic elastomer component is present inan amount from about 5 to about 50 parts by weight per 100 parts byweight of the matrix polymer of the thermoplastic elastomer componentand the thermoplastic polymer component.
 7. A process according to claim2, wherein the rubber component of the thermoplastic elastomer componentis present in an amount from about 10 to about 45 parts by weight per100 parts by weight of the matrix polymer of the thermoplastic elastomercomponent and the thermoplastic polymer component.
 8. A processaccording to claim 7, wherein the crosslinked rubber component of thethermoplastic elastomer component has an average particle size of fromabout 0.1 to about 10 microns, wherein the rubber is crosslinked at atemperature of at least 10° C. higher than the melt temperature of thematrix polymer of the thermoplastic elastomer component, and whereinblending of the thermoplastic elastomer component and the thermoplasticpolymer component is conducted at a temperature greater than 10° C.above the melting point of the thermoplastic polymer component.
 9. Aprocess according to claim 8, wherein the thermoplastic polymercomponent and the matrix polymer of the thermoplastic elastomercomponent, independently, are polybutylene terephthalate, polyethyleneterephthalate, nylon-6, or nylon-6,6.
 10. A process according to claim9, wherein the toughened polymer composition contains less than about 10parts of plasticizer, based on 100 parts by weight of the rubbercomponent of the thermoplastic elastomer component, and wherein therubber component of the thermoplastic elastomer component is present inan amount from 18 to about 45 parts by weight per 100 parts by weight ofthe matrix polymer of the thermoplastic elastomer component and thethermoplastic polymer component.
 11. A method for producing rotationallymolded articles having toughness, comprising the steps of: introducing atoughened polymer composition into a mold of a rotational moldingdevice, said toughened polymer composition comprising a thermoplasticpolymer component, a thermoplastic elastomer component comprising amatrix polymer and a crosslinked rubber component, and optionally acompatibilizer, said matrix polymer being a polyamide or polyester; androtationally molding at least the toughened polymer composition therebyforming an article.
 12. A method according to claim 11, wherein therubber component of the thermoplastic elastomer component is present inan amount from about 2 to about 60 parts by weight per 100 parts byweight of the matrix polymer of the thermoplastic elastomer componentand the thermoplastic polymer component.
 13. A method according to claim12, wherein the thermoplastic polymer component and matrix polymer ofthe thermoplastic elastomer component are, independently, a polyamidederived from polycondensation of a diamine having from 4 to 12 carbonatoms and a dibasic acid having from 4 to 12 carbon atoms; or derivedfrom selfpolycondensation of an amino acid; or derived frompolymerization of a lactam; or a polyester derived from a dicarboxylicacid having from about 2 to about 16 carbon atoms and a diol or diolderivative having from about 2 to about 16 carbon atoms; or derived fromselfcondensation of a hydroxy carboxylic acid; or derived from ringopening polymerization of a lactone, wherein the rubber component of thethermoplastic elastomer component is derived from at least two differentalpha olefin monomers, or is styrene butadiene rubber, hydrogenatedstyrene butadiene rubber, butyl rubber, butyl-paramethyl styrenecopolymer or derivatives thereof, styrenic block copolymer, acrylicrubber, nitrile rubber, hydrogenated nitrile rubber, or ethylenemethacrylate terpolymer rubber, or any combination thereof.
 14. A methodaccording to claim 13, wherein the crosslinked rubber component of thethermoplastic elastomer component has an average particle size of 0.005to about 25 microns, and wherein the thermoplastic elastomer componentand thermoplastic polymer component are melt blended.
 15. A methodaccording to claim 11, wherein said thermoplastic polymer component isnylon-4, nylon-4,6, polyhexamethyleneadipamide (nylon-6,6),polycaprolactam (nylon-6), nylon 6,9, polyhexamethylenesebacamide(nylon-6,10), nylon-11, nylon-12 or copolymers thereof; or polyethyleneterephthalate, polybutylene terephthalate, polyethylene isophthalate, ora block polyetherester, or a combination thereof; and wherein saidrubber component of the thermoplastic elastomer component is an acrylicrubber.
 16. A method according to claim 15, wherein the rubber componentof the thermoplastic elastomer component is present in an amount fromabout 40 to about 90 parts by weight per 100 parts by weight of therubber component and the matrix polymer of the thermoplastic elastomercomponent, and wherein the rubber component of the thermoplasticelastomer component is present in an amount from about 5 to about 50parts by weight per 100 parts by weight of the matrix polymer of thethermoplastic elastomer component and the thermoplastic polymercomponent.
 17. A method according to claim 16, wherein the rubbercomponent of the thermoplastic elastomer component is present in anamount from about 10 to about 45 parts by weight per 100 parts by weightof the matrix polymer of the thermoplastic elastomer component and thethermoplastic polymer component.
 18. A method according to claim 17,wherein the crosslinked rubber component of the thermoplastic elastomercomponent has an average particle size of from about 0.1 to about 10microns, wherein the rubber is crosslinked at a temperature of at least10° C. higher than the melt temperature of the matrix polymer of thethermoplastic elastomer component, and wherein blending of thethermoplastic elastomer component and the thermoplastic polymercomponent is conducted at a temperature greater than 10° C. above themelting point of the thermoplastic polymer component.
 19. A methodaccording to claim 18, wherein the thermoplastic polymer component andthe matrix polymer of the thermoplastic elastomer component,independently, are polybutylene terephthalate, polyethyleneterephthalate, nylon-6, or nylon-6,6.
 20. A method according to claim19, wherein the toughened polymer composition contains less than about10 parts of plasticizer based on 100 parts by weight of the rubbercomponent of the thermoplastic elastomer component, and wherein therubber component of the thermoplastic elastomer component is present inan amount from 18 to about 42 parts by weight per 100 parts by weight ofthe matrix polymer of the thermoplastic elastomer component and thethermoplastic polymer component.
 21. A toughened thermoplasticcomposition, comprising: a blend including a) a thermoplastic polymercomponent, and b) a thermoplastic elastomer component derived from arubber component crosslinked in the presence of a matrix polymer, saidmatrix polymer comprising a polyamide or polyester, the rubber componentbeing present in an amount from about 2 to about 60 parts per 100 partsby weight of the matrix polymer and the thermoplastic polymer component,and wherein the toughened thermoplastic composition optionally comprisesa compatibilizer.
 22. A composition according to claim 21, wherein thethermoplastic polymer component and matrix polymer of the thermoplasticelastomer component are, independently, a polyamide derived frompolycondensation of a diamine having from 4 to 12 carbon atoms and adibasic acid having from 4 to 12 carbon atoms; or derived fromselfpolycondensation of an amino acid; or derived from polymerization ofa lactam; or a polyester derived from a dicarboxylic acid having fromabout 2 to about 16 carbon atoms and a diol or diol derivative havingfrom about 2 to about 16 carbon atoms; or derived from selfcondensationof a hydroxy carboxylic acid; or derived from ring openingpolymerization of a lactone, wherein the rubber component of thethermoplastic elastomer component is derived from at least two differentalpha olefin monomers, or is styrene butadiene rubber, hydrogenatedstyrene butadiene rubber, butyl rubber, butyl-paramethyl styrenecopolymer or derivatives thereof, styrenic block copolymer, acrylicrubber, nitrile rubber, hydrogenated nitrile rubber, or ethylenemethacrylate terpolymer rubber, or any combination thereof.
 23. Acomposition according to claim 22, wherein the crosslinked rubbercomponent of the thermoplastic elastomer component has an averageparticle size of about 0.005 to about 25 microns, and wherein thethermoplastic elastomer component and thermoplastic polymer componentare melt blended.
 24. A composition according to claim 23, wherein saidthermoplastic polymer component is nylon-4, nylon-4,6,polyhexa-methyleneadipamide (nylon-6,6), polycaprolactam (nylon-6),nylon 6,9, polyhexa-methylenesebacamide (nylon-6,10), nylon-11, nylon-12or copolymers thereof; or polyethylene terephthalate, polybutyleneterephthalate, polyethylene isophthalate, or a block polyetherester, ora combination thereof; and wherein said rubber component of thethermoplastic elastomer component is an acrylic rubber.
 25. Acomposition according to claim 24, wherein the rubber component of thethermoplastic elastomer component is present in an amount from about 5to about 50 parts by weight per 100 parts by weight of the matrixpolymer of the thermoplastic elastomer component and the thermoplasticpolymer component.
 26. A composition according to claim 25, wherein therubber component of the thermoplastic elastomer component is present inan amount from 45 to 70 parts by weight per 100 parts by weight of therubber component and the matrix polymer of the thermoplastic elastomercomponent, and wherein the rubber component of the thermoplasticelastomer component is present in an amount from about 10 to about 45parts by weight per 100 parts by weight of the matrix polymer of thethermoplastic elastomer component and the thermoplastic polymercomponent.
 27. A composition according to claim 26, wherein thecrosslinked rubber component of the thermoplastic elastomer componenthas an average particle size of from about 0.1 to about 10 microns,wherein the rubber is crosslinked at a temperature of at least 10° C.higher than the melt temperature of the matrix polymer of thethermoplastic elastomer component, and wherein blending of thethermoplastic elastomer component and thermoplastic polymer component isconducted at a temperature greater than 10° C. above the melting pointof the thermoplastic polymer component.
 28. A composition according toclaim 27, wherein the thermoplastic polymer component and the matrixpolymer of the thermoplastic elastomer component, independently, arepolybutylene terephthalate, polyethylene terephthalate, nylon-6, ornylon-6,6.
 29. A composition according to claim 28, wherein thetoughened composition contains less than about 10 parts of plasticizerbased on 100 parts by weight of the rubber component of thethermoplastic elastomer component, and wherein the rubber component ofthe thermoplastic elastomer component is present in an amount from about18 to about 42 parts per 100 parts by weight of the matrix polymer ofthe thermoplastic elastomer component and the thermoplastic polymercomponent.